Leibnitz, Gottfried Wilhelm (1646-1716). the great philosopher, mathematician, and man of business, was born at Leipzig. His father died when the son was six years old, and from that time the boy educated himself. He was fond of history, learnt Latin, and then taught himself Greek, and logic. Ip 1661, as a law-student at Leipzig, he studied, the new methods of logic which were ousting the scholastic theories, and in 1663 he began to study mathematics. Failing to ,get a degree on account of his youth, he left Leipzig, and obtained employment at Mainz, where he studied alchemy, and became secretary to the Rosicrucians, whose theories he examined. The danger that befell Germany of invasion by France led to his publishing Thoughts on Public Safety (1670), in which he suggested the scheme of France taking Egypt, a scheme which slumbered till revived by Napoleon in 1803. This led to his going to Paris, from which he removed to Amsterdam, and made the acquaintance of Spinoza. He then for many years took charge of the Duke of Brunswick's library at Hanover. From 1712-14 he was at Vienna. He made a calculating-macriine, and his investigations in mathematics resulted in the discovery of differential and integral calculus. His chief philosophical works are the Monadologie (1714), Nouveaux Essais (dialogues on Locke's system), and the Tlteodicee (1710), an attempt to uphold the argument from design in nature. He also wrote much on history and jurisprudence.